Hubble space telescope observations of field ultracool dwarfs at high galactic latitude

R. E. Ryan, P. A. Thorman, H. Yan, X. Fan, L. Yan, M. R. Mechtley, N. P. Hathi, S. H. Cohen, R. A. Windhorst, P. J. McCarthy, D. M. Wittman

Research output: Contribution to journalReview articlepeer-review

34 Scopus citations


We present a sample of 17 newly discovered ultracool dwarf candidates later than M8, drawn from 231.90arcmin2 of Hubble Space Telescope Wide Field Camera 3 infrared imaging. By comparing the observed number counts for 17.5 ≤ J125 ≤ 25.5ABmag to an exponential disk model, we estimate a vertical scale height of zscl = 290 25 (random) 31 (systematic)pc for a binarity fraction of fb = 0. While our estimate is roughly consistent with published results, we suggest that the differences can be attributed to sample properties, with the present sample containing far more substellar objects than previous work. We predict the object counts should peak at J125 24ABmag due to the exponentially declining number density at the edge of the disk. We conclude by arguing that trend in scale height with spectral type may breakdown for brown dwarfs since they do not settle onto the main sequence.

Original languageEnglish (US)
Article number83
JournalAstrophysical Journal
Issue number2
StatePublished - Oct 1 2011


  • Galaxy: stellar content
  • Galaxy: structure
  • brown dwarfs
  • stars: low-mass

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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